The present invention relates to a novel method and system for improving the quality of digester methane gas to enable it to be used effectively and efficiently as a fuel for internal combustion engine - generator systems.
Digester methane gas is generally comprised of a mixture of methane (50-70%), carbon dioxide (30-50%) and varying lesser amounts of oxygen, nitrogen, water, ammonia, hydrogen sulfide and mercaptans and such gas may have a heating value of 400-500 Btu per cubic foot. More typically, digester methane gas is comprised of 52-57% methane, 41-44% carbon dioxide (non-combustible) and 4-7% oxygen, water, ammonia and sulfur compounds. Although it is possible to burn raw digester methane in internal combustion engines, the efficiency of such engines is drastically reduced from that achieved when pipeline methane (1,000 Btu/ft.sup.3) is utilized.